直升机防撞系统的电力线检测方法

使用防撞系统探测电力线,对低能见度条件下直升机的低空飞行安全至关重要。通过理论分析,介绍了电力线的布拉格散射特征。在静态条件下,利用毫米波收发系统对电力线的散射特性进行了试验验证。在运动条件下进行运动补偿,将电力线的布拉格散射回波和输电铁塔的强回波峰进行图像累积,并利用霍夫变换进行电力线提取。试验结果可清晰地检测到电力线,证明了处理模型和方法的正确性。     

机载防撞系统垂直防撞的物理模型

如何准确预测和估算本机与入侵飞机相遇时在最接近点的垂直间隔距离,是机载防撞系统(TCAS)在垂直方向上选择防撞措施的关键问题.采用空间相遇几何学的方法,建立了本机与入侵飞机相遇时垂直防撞的两种物理模型,基于该模型推导出了预测两机之间垂直间隔距离的计算公式,并且进行了计算机仿真.仿真结果表明,该模型能够准确预测本机与入侵飞机相遇时在最接近点的垂直间隔距离.最后,给出了本机在垂直方向上选择防撞措施的决策咨询条件和逻辑处理流程.     

A Novel Approach towards the Designing of an Antenna for Aircraft Collision Avoidance System

TCAS/ACAS (Traffic/Aircraft Collision Avoidance System) is an airborne system designed to increase cockpit awareness of nearby aircraft and to service as a last defense against mid-air collisions between the aircrafts. In the existing system, four monopole stub elements are used as TCAS directional antenna and one blade type element is used as TCAS Omni-directional antenna. The transmission and reception frequencies of the TCAS antenna are 1.03G Hz and 1.09G Hz respectively. The existing TCAS antenna has some drawbacks such as low gain, large beamwidth, frequency and beam tuning/scanning issues etc. Antenna issues like unwanted signals reception may create difficulties in identifying the possible threats. In this paper, the focus is on the design and development of a novel Microstrip Antenna Array which can be used for TCAS/ACAS application. Two proposed antenna models are presented here – a Unit Element Dual Feed Microstrip Dual Patch Slotted Antenna and a Compact Microstrip Antenna Array. These are designed in CST tool to meet the current needs of aircraft Collision Avoidance System and to overcome the possible limitations associated with the existing techniques. The performance and other antenna characteristics have been explored from the simulation results followed by the antenna fabrication and measurement. A good Reflection Coefficient and VSWR with proper 50 Ω Impedance Matching, narrow Beamwidth, perfect Directional Radiation Pattern, high Gain and Directivity at the operating frequencies make this proposed antenna a good candidate for TCAS application. The proposed antenna would be expected to meet the requirements of the advanced avionics standards in terms of design simplicity, lightweight and high performance.     

一种车载毫米波列车防撞雷达系统研究

列车防撞雷达是保障铁路行车安全的一种重要设备,该文针对列车防撞应用需求中的低成本实现目标方位角度高精度测量难题,采用了基于开关切换的数字阵列天线和频率步进高分辨波形设计方法,分析了收发天线的天线方向图和频率步进合成宽带信号幅相误差补偿问题,并构建了一种低成本车载毫米波防撞雷达系统,进行了原理样机外场实验。实验结果表明该样机系统达到了较高的距离分辨率和角度测量精度,可有效分辨铁轨内外目标。      

A Novel Collision Sup ervision and Avoidance Algorithm for Scalable MAC of Vehicular Networks

In order to meet low-latency and ultra-reliable requirements on safety services in vehicular networks, this paper proposes a novel Collision supervision and avoidance (CSA) algorithm for the contention based scalable media access control protocol. The two-dimensional Markov chain model of adaptive backoff state transition criterion in CSA has been built, which could efficiently match the backoff states of nodes to the dynamic changes of vehicular networks. The scalable transmissions can be achieved through supervised trend and matching backoff mechanisms with three adaptive backoff modes. The packet transmit probabilities for the backoff modes have been derived with the theoretical result of the enhanced throughput. The simulation results show the remarkable scalability performance such as normalized throughput >0.92, PDR >86％ and delay <6.5ms even in the high-density and high-mobility environment.     

碰撞避让系统的仿真教学实践研究

本文以碰撞避让系统的仿真为教学实践实例,介绍利用Matlab和PreScan仿真软件搭建了碰撞避让系统的虚拟实验平台,使学生从原理、方法设计及技术需求等多个方面学习掌握智能交通技术,从教学内容和实践方法上满足社会发展对学生能力的要求.     

民机空中交通警戒与防撞系统目标跟踪算法

空中交通警戒与防撞系统(TCAS)是航空电子综合环境监视系统的一个重要组成部分,它能有效降低空中飞行器间的碰撞威胁,对于提高飞行安全有着非常重要的意义。TCAS是一种不依赖地面设备的空中交通防撞系统。它能够探测在其领域内装有空中交通管制应答机的飞机,向驾驶员报告潜在的相撞目标。目标跟踪是TCAS的一个重要模块,能提供目标的飞行状态信息,并对目标的未来飞行状态进行预测。对空中目标进行稳定、高精确度的跟踪是目标跟踪模块的重要任务。本文介绍了基于扩展卡尔曼和交互式多模型(IMM-EKF)的目标跟踪算法,实现对目标的精确跟踪。通过仿真验证,证明算法能实现精确的目标跟踪,对防止空中相撞起到了积极作用。     

利用相邻帧和背景信息的运动对象检测

 运动对象检测是智能视频监控的基础,现有的运动对象检测算法在实时性和检测精度方面仍有待提高,本文在分析相邻帧间的亮度变化基础上,提出了基于三阶中心矩统计分布的背景点阈值计算方法,给出了抗噪声干扰的背景维护模型,最后综合利用时间差分法和背景减法进行运动对象检测,为了提高检测精度使用了形态学的腐蚀与扩张处理.对室内、室外序列以及标准序列的测试结果表明,本文算法速度快、抗噪声能力强,能够检测出被遮挡的运动对象.     

LFMCW雷达在吊车防撞高压线系统中的应用

线性调频雷达在距离测量方面有着广泛的应用。本文介绍了一种利用X波段线性调频连续波雷达来探测高压线以防止吊车触电的技术。首先对线性调频雷达测距的原理作了简要分析,然后对雷达前端的硬件实现以及软件算法流程进行了较具体的描述,最后经过实际测试,验证了系统的稳定性和距离测量的准确性。     

编队飞行防撞系统防撞模型研究

针对飞机编队飞行防撞系统的功能要求,采用时间碰撞威胁度和空间碰撞威胁度的方法建立了编队飞行碰撞威胁的探测模型,给出了基于机载防撞系统的编队飞行模拟测试系统的仿真方法和测试方案,并且进行了计算机仿真和测试.仿真结果表明,该编队飞机防撞模型能够为飞行员提供侵犯告警咨询信息和正确编队的位置指示.     

A Novel Dynamic Obstacle Avoidance Algorithm Based on Collision Time Histogram

Robot path planning in uncertain dynamic environment is a hot issue in the field of Unmanned ground vehicle (UGV). Starting from the practical demands of UGV, we propose a novel dynamic obstacle avoidance al-gorithm based on Collision time histogram (CTH). Given current steering angle, an effective collision check model, which is called Collision check circles (CCC), is firstly cal-culated. The local environment information is then com-bined with CCC to generate the proposed CTH. The non-holonomic nature of the vehicle is embedded in this pro-cess. Finally, the proposed algorithm calculates the execut-ing steering angle by considering both the CTH and the target point. Extensive experiments and comparisons are conducted to evaluate the performance of the proposed al-gorithm. Simulation experiments are firstly conducted to verify its feasibility. Furthermore, real-world experiment is conducted to verify its effectiveness. Experimental results demonstrate the practical value of the proposed algorithm.     

ADS-B技术在通用航空避撞系统中应用研究

分析了 ADS-B 技术及其在运输航空监视管理系统、通用航空监视管理系统、无人机监视管理系统和避撞系统中应用情况。分析了构建通用航空避撞系统的必要性和构建基于 ADS-B 的通用航空避撞系统的可行性及其优势;研究表明基于 ADS-B 技术的通用航空避撞系统是非常符合我国通用航空特点和需求,在性能上较 TCAS 会有更多优势,除了用于通用航空飞机自身相互避撞外,还可实现通用航空飞机与无人机、运输航空飞机以及地面建筑物和障碍物的避撞。基于 ADS-B 技术对通用航空避撞系统总体构建,包括硬件部分、软件部分、数据部分和通用航空避撞系统规划。     

引入自动驾驶仪时空中交通防撞系统的仿真

空中交通防撞的主要功能是对本机和入侵目标机位置的预测以及在预测后对冲突的处理。在防撞过程中,入侵飞机的轨迹突然发生比较大的机动,则原有的防撞策略失效。2009年欧洲航空安全局认证通过了自动驾驶仪在避撞时与防撞系统耦合的方法,使问题得到了一定的解决。对避撞系统加入自动驾驶仪的方法进行了研究建模,并且对解决的情况进行了仿真,为民航空中交通避撞提出了一种新的思路。     

Hierarchical Longitudinal Controller for Rear-End Collision Avoidance

Rear-end collision is a very serious problem in modern traffic situations, and there have been a great number of research reports on the longitudinal control method for road vehicles. In many cases, however, the control problem is formulated under platoon configuration and for some predictable noncollision situations. For predictable collision situations, regional and hierarchical approaches have been employed, but these approaches render difficulties due to ignorance for modeling error and logical error in a decision process. In this paper, the vehicle control for collision avoidance is studied with two control objectives, i.e., minimization of the safety distance error and regulation of the relative velocity between two vehicles. For this, a longitudinal controller using terminal sliding mode (TSM) with hierarchical structure is proposed for rear-end collision avoidance. The TSM is employed to achieve convergence in finite time, while the hierarchical approach is used for the system to accommodate the intelligence of the driver to handle various situations. The effectiveness of the proposed control scheme is verified by software simulations     

基于满意度移动模型的点军标显示自动避让方法

将点军标显示避让问题当作空间竞争问题求解,提出一种基于社会活动领域的满意度移动模型的点军标自动避让方法。该方法以点军标显示最小外接矩形重叠区域大小作为军标满意度,将点军标配置位置的四方向领域作为移动备选位置,通过多次迭代使得各点军标位于其满意度最大位置,将此满意度最大的点军标集合作为避让标绘的结果。实验结果表明,该方法能够较好解决点军标显示占位冲突,实现自动避让标绘。     

SELECT: Self-Learning Collision Avoidance for Wireless Networks

The limited number of orthogonal channels and autonomous installations of hot spots and home wireless networks often leave neighboring 802.11 basic service sets (BSSs) operating on the same or overlapping channels, therefore interfering with each other. However, the 802.11 medium access control (MAC) does not work well in resolving inter-BSS interference due to the well-known hidden/exposed-receiver problem, which has been haunting the research community for more than a decade. In this paper, we propose SELECT, an effective and efficient self-learning collision avoidance strategy to address the hidden/exposed-receiver problem in 802.11 wireless networks. SELECT is based on the observation that carrier sense with received signal strength (RSS) measurements at the sender and the receiver can be strongly correlated. A SELECT-enabled sender exploits such correlation using an automated online learning algorithm and makes an informed judgment of the channel availability at the intended receiver. SELECT achieves collision avoidance at packet-level time granularity, involves zero communication overhead, and easily integrates with the 802.11 distributed coordination function (DCF). Our evaluation in analysis, simulations, and prototype experiments show that SELECT addresses the hidden/exposed-receiver problem well. In typical hidden/exposed-receiver scenarios, SELECT improves the throughput by up to 140 percent and the channel access success ratio by up to 302 percent while almost completely eliminating contention-induced data packet drops.     

无人机动态避撞区建模方法研究

针对现有方法采用定值飞行间隔确定避撞区域对空域利用不足的问题,提出一种动态、实时建立避撞区域的方法。根据无人机的机动约束,无人机的碰撞区域以及飞机之间的相对位置、相对速度等信息,实时建立避撞区包络。由于动态考虑了无人机与入侵飞机对避撞区的影响因素,提高了所建包络的针对性,缩小了避撞区包络所占的空域面积,不仅避免了一些不必要的规避机动,而且还可以使繁忙的空域得到更合理的利用。仿真结果验证了所建动态避撞区的有效性。     

毫米波汽车防撞雷达系统中数字信号处理机的设计

测距测速是雷达的基本应用之一。文章设计了基于DSP芯片TMS320VC5402的数字信号处理机,对汽车防撞雷达系统接收到的回波信号进行了实时采样和分析并实时计算出目标的距离和速度。实验表明,该信号处理机工作稳定可靠,满足了汽车防撞雷达系统对信号处理的实时性要求。     

针对动态障碍物的无人机最优避撞策略

复杂动态环境下自主避障能力已成为无人机亟待解决的关键问题.针对现有避障算法通过调向或调速进行规避障碍的缺点,基于速度障碍法,提出一种同时调向与调速的混合避障策略.首先,根据速度障碍法原理,判断无人机与动态障碍物是否存在飞行冲突;然后,分别在单动态障碍物和多动态障碍物场景下,利用数学公式精确推导出无人机避障所需要调整的航...